Cycles texture stretching past the edge
Cylces does have the bad habit of stretching the pixels past the edges of the image.



One quick solution is editing your image and adding a black or transparent border all around. (All you need is one pixel wide ...). 


Cycles will then repeat that border...

Or you can create a file that is a black border around a transparent image and use that as a factor on a mix node to create a color frame past your image:



or a different shader: